I am a guy who is trying to correct many misleading theories and practices for the railroad industry. Curve- degree-radius measurement is one of them.
Please point out one thing that is wrong in my statements. I bet you cannot do it.
What I can say is that the measurements you did before were wrong. If you continue to do that you should feel sorry for your pay check.
worker,
What measurements are you referring to as being wrong? Who are you addressing?
Bucyrus:“Who are you addressing?”
Worker: My message is to Mudchicken’s message :"
I don’t think Mr. Moderator wants me too have a war of wits with an unarmed individual. Hopefully worker hops on the next rubber-tired turnip wagon and prattles on.
I needed a good laugh this morning."
Worker’s answer:"
I am a guy who is trying to correct many misleading theories and practices for the railroad industry. Curve- degree-radius measurement is one of them.
Please point out one thing that is wrong in my statements. I bet you cannot do it.
What I can say is that the measurements you did before were wrong. If you continue to do that you should feel sorry for your pay check"
Worker,
I generally understand what you said about curves, but what do you mean when you said this?–
“What I can say is that the measurements you did before were wrong. If you continue to do that you should feel sorry for your pay check”
What measurements are you referring to that Mudchicken did?
There will be no answer to that, since the poster complaining has evidenced little or no knowledge of surveying so far, among other things. I too am a little in the dark as to what worker’s actual point is, though his or her confidence seems unbounded. I have seen that phenomenon before from time to time, to which my response has always been “make your case” with specifics.
With that observation, I will make some more general observations which will be familiar to some forum participants in one manner or another.
Chuck, you did intend to say a 100 link chain, did you not? For the benefit of non-surveyors, I will remind them that each link in a surveyor’s chain is 7.92 inches long, which makes a chain 792 inches (66 feet) long.
What I referred to was something to measure to the next 100 foot station interval, which appears to have been pretty much standard procedure in staking a curve. Of course, these days that would be accomplished with the precision distance measurement capability of a modern surveyor’s station; how specifically railroad surveyors worked it in the past I don’t know.
A chain is four rods in length, 66 feet, as you note. Land surveying (boundaries and area) is likely somewhat different from engineering surveying as the goals are not perfectly aligned and I would suspect the tools of engineering surveying might differ a bit from meets and bounds surveying. That being said, I was referring to a generic hundred-foot chain, not a surveyor’s chain.
What is to this day utterly amazing to me is how accurate many of the 19th century surveys turned out to be when resurveyed with modern instruments of nominally much better accuracy.
BTW, I’ll add that I am flabbergasted by the capabilities of the modern total surveying station and what an advantage that gives to the construction engineer. Progress that really helps!
I may be on thin ice here…
Land surveying with a chain was a way of getting away from “meets and bounds” and thus closer to engineering survey than you think. The 100 foot baseline for degree of curvature was likely derived from the push to decimal measurements.
FWIW, the 66 foot chain is the origin of the size of an acre (10 square chains) and the statute mile (80 chains).
Very true.
ChuckCobleigh:
Your message clarifies the misunderstanding among us and makes the discussion productive. I am talking about using AAR’s (Association of American Railroads) method (100-foot-chord) to measure the DEGREE or Radius of curvature for a curved rail with zero information about the curve. See sketch below for AAR’s definition. What I found is that the method is a misleading.
(Note: the sketch cannot be shown out here, it the common 100ft method)
What you are talking about is constructing or measuring a curved rail on site with the DEGREE and radius of curvature given. With my limited knowledge in survey, I know there are three methods that can be used to build stations on the curve, such as the tangent offset method. That explains why “they are fanatical about spirals” because the radius of spirals are complicated by spiral design. Am I correct?
I am not a surveyor and you know it. My trouble begins when I want to know if a curved rail is really constructed to the design. That is, if the radius is really the one specified in the design.
Anyway, see if you can do this. If we have a curved rail with a very large radius of curvature (say is about 7,000 meters), and all the records for the curved rail are lost. We don’t know nothing about the radius or degree. Can you (using your method) measure the unknown curved rail to determine the radius of curvature with ease and accuracy? I will certainly learn something from you if you can do it because I came up with a simple method to measure the radius of curvature for all the unknown curved rails.
Certainly, there are tangents, curves and spirals in the rail system. However, a spiral is another misleading issue in the railroad industry. The reason for a spiral to be used, I found, is that there is a jump in radii (R) of curvature
Reading the above posts about railroad track that curves leaves me puzzled. There seems to be (or at least no one admits to knowing) how such a track can be built. In fact, the most logical conclusion from the posts themselves would be that such a track is impossible. But of course we do have railroad tracks and some of them are curved.
Degree of Curve/ Chord Definition is extremely simple and you can backfigure radius with simple trig and geometry. The method and definition came from our military engineers (artillery) who were in abundance, especially post civil war via West Point & Jefferson Barracks. Calculating curve length is much easier using degree of curve than using radius and the laying out of curves in the field is also much quicker.
John WR:
For your information, there are still more misleading issues in the railroad industry at the present, I think.
You mentioned why no one knows it. I don’t know why. However, there are thousands of trains running everyday. Railroad people depend heavily on testing to determine the speed of a train. So defects in design can be compensated by lowing the running speed of a train. Thus, a train can run but with low efficiency, such as high maintenance cost, high energy consumption, etc.
Thanks, Mud Chicken. I looked up “degree of curve” on the internet and now I can see that the calculation can be done. I have to say I wouldn’t call it “extremely simple” but perhaps that is because I am extremely simple.
John
I think there are misleading issues in just about every aspect of our lives. By “misleading issues” I mean issues that seem simple but in fact are more complicated than they appear to be. However, to say that an issue is more complicated than it appears to be does not mean that it is incapable of resolution.
Exactly!
I found a couple of old texts on railroad surveying in Google Books which enlightened me on tried and true techniques, which is something which might help our new poster get some insight into “how it’s done” and why it’s not really magic like it seems, but just the systematic application of fairly fundamental mathematical principles. That, of course, is one good definition of what engineers do, or at least that’s been my take for a long time. In fact, I probably cannot take credit for the expression, as I am sure I heard it early on in one or more engineering classes oh so long ago.
I might suggest to him or her the getting hold of a good text on railroad engineering, which doesn’t have to even be all that recent. I have a 60-year-old book by William Hay of the U of Ill Railway CE department that I have had for over 30 years which is an interesting read for a retired EE (yes, we had to take the same fundamentals courses that the other disciplines did then, plus two upper-division electives in CE or ME, something that seems to have gone by the way for EEs these days, I am told). Perhaps the poster could find some illuminating discussions of spiral easement sections of curves.
Surveyors and those polite engineers have certainly refined the art of track alignment over the years and
ChuckCobleigh,
As I said, I am not a surveyor, and I don’t want to dig into the survey area to re-invent the wheel. However, I did invent a device to measure the radius of curvature for the curves and spirals. You make me wonder how many curved rails (spirals) constructed for the railroad would have the radius as specified in the design if I measure them with my device. We trust you but we need to check. That is what they say.
You also mentioned: “Perhaps the poster could find some illuminating discussions of spiral easement sections of curves.”
I did re-invent the wheel in spirals. I encourage you to challenge my invention. After digging into that many historical files, do you find anything wrong in my invention? If so, come to challenge me.
I will gladly defer to the engineers on this thread, but I don’t think that any rail was ever rolled or cast in a curve of specific radius. The rail would be spiked into place at one end and pulled into the desired curve and then spiked into place.
Worker,
Why don’t you show us the device that you invented, explain how it works, and tell us what benefit it provides?
Worker seems very confused, even if he feels certain in his own mind.
It is very easy to determine the degree of curve. You need three people, a piece of string 62 feet long, and a short ruler measured in inches. Hold each end of the string against the gauge side of the rail and pull it tight. The distance from the center of the string (31’ from each end) to the gauge in inches is the degree of curve. No need to head half a mile off in the trees to find the center of the curve. If you check several places along the curve there will almost certainly be minor variations. Occasionally you might also find compound curves when the alignment was constrained by outside obstacles.
Nor do I understand what he thinks the spiral easements are. When travelling at any speed you don’t want to suddenly change from going straight to turning. Same when driving a car - you don’t instantly yank the steering wheel over. The spiral easement is also where the superelevation transitions from nil to whatever is specified for the train speeds and degree of curve. On compound curves another connecting spiral may be required if the respective degrees of curve are significantly different.
The degree of curve and spirals that the railroads use are slightly different from those used by the highway engineers.
John
Rolled straight, for sure, and in regular heavy rail, just laid down and spiked in place, unless there is a rare exception. Transit, though, with high-degree curves, has been known to put rail through a portable curve bender to get those tight alignments. I’m not able to find the site referenced in a much earlier forum post, but the machines are definitely out there. As I recall, we are talking a three-roller tube bender on megasteroids.